Trimming mechanism for grinding wheels



March 28, 1944. R.'J. BULLOWS 2,345,323

TRIMMING MECHANISM Fon GRINDING WHEELS Filed Dec. 26. 1941 s sheets-sheet 1 Figi March 28, 1944. R, 1 BuLLows TRIMMING MECHANISM FOR GRINDING WHEELS 3 Sheets-Sheet 2 Filed Dec. 26, 1941 Pig @www

March 23, 1944. R. BULLOWS 2,345,323

TRIMMING MECHANISM FOR GRINDING WHEELS med Deo. ze, 1941 3 sheets-sheet 3 Patented Mar. 28, 1944 TRIMMING MECHANISM FOR GRINDING WHEELS Richard John Bullows, Shirley, near Birmingham, England, assigner to The Gear Grinding Company Limited, Shirley, near Birmingham,

England Application December 26, 1941, Serial No. 424,557 In Great Britain February 22, 1941 4 Claims.

This invention has for its object to provide improved means for trimming the working surfaces of formed grinding wheels used in the grinding to predetermined shapes of the faces of gear wheel teeth, splined shafts, screw threads and the like.

In the accompanying sheets of explanatory drawings:

Figure 1 is a sectional side elevation of trimming mechanism constructed in accordance with the invention.

Figure 2 is a section on the line 2--2 of Figure 1.

Figures 3, 4 and 5 are respectively opposite end elevations and a plan of the mechanism shown in Figure 1.

Figure 6 is a view illustrating the cross sectional form of the part of a grinding wheel to be trimmed by the mechanism shown in Fig-- ures 1 to 5.

The mechanism shown in Figures 1 to 5 is adapted for trimming the working surfaces of a grinding wheel a, used for grinding the teeth of gear wheels. As shown in Figure 6 the grinding Wheel a has a pair of curved side surfaces b, a peripheral surface c, and rounded edges d between the side and peripheral surfaces, the surfaces b, c and d being shaped to correspond respectively with the adjacent faces of a pair of gear teeth, the base of the space between these faces, and a pair of rounded fillets situated at the junctions of the tooth faces and the base.

In carrying the invention into effect as shown, I employ a lever-like shaft consisting of long and short parts f, e, which at their adjacent ends are formed integrally with each other or secured together, the shaft being oscillatable able about its own axis in the manner hereinafter described. The short part e of lthe shaft is adapted to carry a pointed diamond or other suitable trimming tool g, and is so cranked or otherwise shaped that the tool can be arranged to extend radially inwards with its operative end situated at a distance from the axis of oscillation of the shaft corresponding to the radii of the two rounded edges d of the grinding wheel a. The shaft e, f, is rotatably mounted in any convenient bearing h which surrounds a portion of the long part f of the shaft, and which is provided at the end adjacent to the short part e of the shaft with a fork-shaped extension i, the latter being connected by a pair of coaxial and horizontal pivots :i to a fork-shaped support k which is carried by a vertical pivot m. The' pivots y, m, enable the bearing h and shaft e, f

to be rocked in each of two planes at right angles to each other in a hollow body part 1L through which the shaft extends, the vertical pivot fm, being mounted on a bracket o secured to one side of the body part. If desired the bearing h may have associated with it any convenient resiliently mounted supporting member as p or a supporting spring. The end of the long part f oi' the shaft remote from the tool g lies between and can co-operate with each in turn of the edges of a pair of fixed templates q adjustably mounted on the adjacent end of the body part n, the edges of these templates being shaped to corerspond with the form to be imparted to the two curved side f faces b of the grinding wheel a. This end of the shaft is preferably provided with a roller r through which it canv make contact with the templates q.

At any convenient position on the long part f of the shaft between the bearing h and the roller r is formed or secured a short crank s, herein termed the driven crank, and above it within the body part n of the mechanism is mounted a rather larger crank t herein termed the driving crank, the latter being adapted to be actuated by any convenient means; In the example shown the driving crank t is secured on a stub shaft u journalled in one side of the body part n, and is adapted to be actuated through a wormv and form wheel o1 by a hand wheel The relative disposition of the two cranks s, t, is such that in the central position of the mechanism their centre lines are in the same plane as shown. The two cranks s, t, are interconnected by a connecting rod x, the latter having universal pivotal connections x1, x2 with the cranks. The end of the connecting rod .1: adjacent to the driving crank t is formed with an extension y, and in association with this extension is a controlling spring 2 which in the example shown has the form of a helical compression spring. This spring 2 is mounted on a bar 3 secured in the body part n, and parallel with this bar is secured in the body part another bar 4 on which are mounted a pair of slides 5 having apertured vlateral projections 6 through which the bar 3 passes, the said projections being adapted to abut at their adjacent sides against opposite endsof the compression spring, and at their other sides against adjustable stops 'l on the body part n. Also each of the slide projections 6 is connected by a slotted linkv 8 to the outer end of the extension y of the connecting rod When the connecting rod a: is moved in one direction from its central position it actuates one of the slides 5 through one of the links 8 against the resistance of the spring 2, and when moved in the opposite direction it causes movement of the other slide through the other link also against the resistance of the said spring.

On the long part y'fof the rshaft e, ff, between the driven crank sand the roller r which cooperates with the templates q I mount a control member 9 which does not itself rotate but allows rotation of the shaft. The control .member M9 is provided with a pair of adjustable stops "I situated at opposite sides of the axis of the shaft e, f, and the driven crank as sis .providedat lits opposite sides with abutments fIiI `which/causengage the stops. The control=membcr9-is carried by any convenient means which will permit the required rocking of the shaft e, f, infeach-of tWo planes at right angles to each other. Thus, fin the example shown the control member 9 is embraced by and pivotally attached to the-open'end of a fork I2 whose other end has :a universal pivotal connection I3 .with one end of .a framelike arm I4, the other'end .of the latter being pivoted to a stationary member I5, within the body part n, on an axisat rightangles to that of theshaft e, f. The .arm .I4 is therefore capable of swinging .only ,about a pivot axis at right angles to the axis of theshaft, butthe fork I2 can swing 'in any direction. Moreover the fork I2 is connected by a -helical .tension spring z to the outer end of the extension .yof the connecting rod Furtherthere is ,providedpn .the body part n an adjustable stop .I6 against which the end of the arm I4 connected to .the fork I2 can abut under the action of the springe.

To elucidate the mode of operation of the above described mechanism lit is convenient to start with the cranks s, t, and connecting rod m .in their central positions as shown, and the point of the `tool g in contact with the centre of .the periphery cof thevgrinding Wheel a, the axis of the shaft e, f, then vlying in the central plane ofthe grinding Wheel, and the arm I 4 being in contact with the stop I6. The rst effect `of movement ofthe driving crank t ineither direction .is to rock the connecting rod :r .about its pivotal connection with the driving crank. This rocking movement of the connecting rod x, which takes place as a result of the resistance of the spring 2 .to movement of the connecting rod extension y, .has the effect of .swinging theshaft e, f, in a horizontal plane about the pivot m and so-causing the pointof the tool g to move across one-half of the wheel periphery c until arrested by contact of the roller r with the edge of one of the templates q. Continued movementof the driving crank t causes the driven crank s to ro- Ytate the shaft ze, f, about -its axis and so cause the .tool gto trimvone of therounded edges d of the grinding wheel va, .to the required radius. This movementof the drivencrank s is arrested when vone of the crank abutment-s II makes contact with ,one of the stops I0 -on the control member 9. Thereafter .further movement of the driving crank t causes the shaft @,j, to -swingin a manner determined by the interaction of .the roller rwith the edge of `the adjacent template q, so .causing the tool gto traverse the corresponding side face-bof the grinding wheel a. During .this'movement the roller r iskeptfin kcontact with vthe said template q .by the vjoint forces vtransmitted by the .connecting rod .1J-and the spring z which connects the latter to the control member 9. :Whenithe tool g reaches the end of itspath further motion .is prevented bythe enga-gement of a convenient part of the mechanism, such as one side of the driving crank t with a stop I1. At this stage the motion of the driving crank t is reversed, and the tool g is caused to re-trace its path until it reaches its initial position. Continued movement of th ecrank t beyond this position causes the shaftroller 1' to swing into contact with the other template q and to repeat the Y above described sequence of actions on the other "venientin practice to start the trimming operation at one end "of the path of the tool g where ythelatter wouldcommence its action at one side y.of vthe wheelc, traverse one of the curved faces b, then pass around one of the rounded edges d and across the periphery c, and after rounding `the other rounded edge sweep .over Athe other curved side surface.

'By means for va'mechanism as aabove described I am able to eiect the trimming inf the sidefa'ces and periphery 4of Va grinding wheel I:by means of a single tool and thereby ensure perfect continuity of the .treatment o'f Vdifferentfportions of the working surfaces of the wheel, a condition which is diflicult to lobtain when 'two :or imore separate tools acting on 'different parts of '.'the wheel are used. When as has been .more :usual in the past a .plurality of tools aroused, eachtool is apt to wear unequally at different sidesIof'its point, with a result that .the .wheelvfaces acted onby the tools-are not perfect @reproductions-of the shapes corresponding to the templates. By my invention this .conditionfis also obviated or minimised, and the wear is more symmetrically distributed over 'the :active portions .of the tool.

The invention is not limited to the example above described as subordinate detailsof construction or ,arrangement may be varied to suit different requirements. If desired 1I may farrange for the mechanism to be actu'ated'automatically instead `,of by. hand. .Also the bodypart may be .mounted `on any conveniently arranged slide vor slides enabling vthe tool to be brought into appropriaterelationship with the Wheel lto be trimmed. Moreover a single appropriately shaped template .may Abe used instead o'f a pair of templates/as abovedescribed. Further the invention is not limited to the particular use above described as it :is .equally applicable with appropriate modification of detail to `the trimming of wheels required for .grinding spline shafts, -screw threads,:and the like.

Having thus described -my invention what I claim as new and desire to secure `by yLetters Patent'is:

1. A Ygrinding wheel trimming mechanism comprising the combination of a -shaft adaptedat one end to carry'a trimming tool and attheother end lto co-operate with 'at least one template, means for supporting theshaft whereby it can be osclllated about its own axis and also in each of .two planes at right angles to each other, la driving crank, a Y.driven crank on the shaft, a connecting Vrod linterconnecting the 1two cranks, a non-rotatable member mounted lon `the shaft at a positionbetween -thedriven crank-andthe end of rthe'shaft ladapted to 'co-operate withthe template,rinterengageable partson the said member and vdriven .crank `for limiting the angular movement lof the ilatter crank, a Ispringinterconnesting "the said lmember and an "extension yof the end of the connecting rod adjacent to the driving crank, and a second spring adapted to oppose movement of the said extension.

2. A grinding Wheel trimming mechanism as claimed in claim 1 and having in combination a fork-embracing and pivotally connected to the non-rotatable member on the shaft, and an arm pivotally supported at one end on an axis at right angles to the axis of the shaft, the other end of the arm having a universal pivotal connection with the fork.

3. A grinding wheel trimming mechanism as claimed in claim 1 and having in combination a hollow body part through which the shaft extends, a bar secured in the body part and having the second spring mounted on it, this spring having the form of a helical compression spring, another and parallel bar secured in the body part, a pair of slides mounted on the latter bar and adapted to abut against opposite ends of the said second spring, and slotted links connecting the slides to the outer end of the extension of the connecting rod so that either slide can be actuated by the connecting rod against the resistance of the said second spring.

4. A grinding wheel trimming mechanism comprising the combination of a shaft adapted to carry at one end a trimming tool and at the other` end to co-operate with at least one template, means for supporting the shaft whereby it can be osoillated about its own axis and also in each of two planes at right angles to each other, a driving crank, a driven crank on the shaft, a connecting rod interconnecting the two cranks, and controlling means whereby the tool under the action of the driving crank is caused to traverse a desired path determined in part by the template, the means for supporting the shaft having in combination a bearing surrounding the shaft at a position near the end adapted to carry the trimming tool, and a supporting member which is movable about a vertical axis and to which the bearing is pivoted on a horizontal axis, the shaft being shaped so that the tool can be arranged to extend radially inwards with its operative end spaced from the axis of the shaft,

RICHARD JOHN BULLOWS. 

